City Hall's vast machinery went into overdrive after police questioned Sheriff Ross Mirkarimi about a Dec. 31 argument during which he bruised wife Eliana Lopez's right arm. A neighbor videotaped the bruise and later contacted the police. District Attorney George Gascón filed three misdemeanor charges against Mirkarimi for domestic violence battery of his wife, child endangerment (because the couple's son was present) and dissuading a witness (presumably Lopez). San Francisco truly is the city that knows how - to overreact.

In March, Mirkarimi pleaded guilty to one misdemeanor charge of false imprisonment - a plea bargain that usually allows law enforcement officers to keep their jobs.

Mayor Ed Lee asked the newly elected sheriff to resign. When Mirkarimi refused, Lee asked the city Ethics Commission to consider "official misconduct" charges against the sheriff and recommend whether the Board of Supervisors should fire him. In August, the ethics panel ruled 4-1 against Mirkarimi. On Tuesday, the supervisors will vote on Mirkarimi's fate. If nine supes vote against him, Mirkarimi will lose his post.

Insiders have trouble naming three supes likely to vote to keep Mirkarimi or conjure a legal excuse to recuse themselves. Any politician savvy enough to win elective office in City Hall probably does not want to anger anti-domestic violence groups.

Besides, to many voters, this issue is a no-brainer: Mirkarimi pleaded guilty. As Ethics Commissioner Paul Renne put it, "Voters would be shocked if we said a public official who had pleaded guilty to false imprisonment was not guilty of official misconduct."

Under different circumstances, I would expect to make the same arguments myself.

But the circumstances in this drama demand context.

To start, Mirkarimi bruised his wife's arm. As far as we know, that's it. I believe it is possible for a spouse to bruise a spouse's arm without committing domestic violence.

When in doubt, ask the spouse. Lopez testified under oath that her husband never hurt her. She never asked authorities to intervene. She did not want the restraining order that kept the couple apart until it was lifted after seven months.

Advocates for domestic violence victims had contended that victims often lie out of fear, under an abuser's sway or to protect their accusers. But after Lopez, a telenovela actress, took the couple's son for a months-long hiatus in her native Venezuela, she returned with a fierce commitment to resume her marriage despite the system's efforts to break her family apart.

Lee told The Chronicle Editorial Board Thursday that he wishes the Ethics Commission hearings hadn't taken so long. Mirkarimi's lawyers aren't exactly slouches at delaying tactics. But these hearings never would have taken as long as they did had the mayor not thrown in loose charges. The mayor's amended complaint charged that Mirkarimi had told Lopez that he is "powerful," for example, and that Mirkarimi tried to dissuade neighbors from testifying.

Investigators were sent out to investigate these stories. In overcharging Mirkarimi, Lee dumped on the commission the unhappy job of wading through depositions of neighbors, a campaign consultant, even an old Mirkarimi girlfriend. These side charges gave way to an orgy of hearsay and character assassination.

I've heard Mirkarimi critics repeat some of the side charges against Mirkarimi as fact. They should know that after months of investigation, the commissioners found Mirkarimi's official misconduct to consist of bruising his wife's arm, a violation of her personal liberty, and pleading guilty to a criminal charge. The other charges did not stick.

Commission Chairman Benjamin Hur dissented. He said that he found Mirkarimi's behavior to be "egregious," but there was no link between his actions and his "official" duties. Indeed, Mirkarimi hadn't even been sworn in as sheriff on New Year's Eve.

At City Hall, there should be a plaque that reads, "The more personal and less official a matter is, the more City Hall wants to do something about it."